1. Field of the Invention
This invention relates generally to the storage of digital voice message data in memory. More particularly, it relates to managed storage of new voice messages over previously stored older voice messages to provide a virtually endless ability to store new voice messages in a digital voice messaging system even after the voice message memory is filled.
2. Background of Related Art
Voice messaging has become an everyday requirement in today's society. Early voice messaging systems comprised magnetic cassette tapes which recorded a significant amount of voice messages, e.g., 60 minutes of voice messages. However, cassette tapes were disadvantageous because of the mechanics and time required to fast-forward and rewind the cassette tapes to the storage points of individual messages. Moreover, cassette tape voice message systems were not best suited in a business environment where multiple persons may utilize a common telephone switching system or voice messaging system.
More recently, particularly as the size of memory has increased in density while at the same time decreased in price, digital voice messaging systems have become commonplace. Voice compression techniques such as linear predictive coding (LPC) or code-excited linear predictive (CELP) coding utilized by some conventional digital voice messaging systems maximized the length of voice messages which could be stored in the finite amount of memory provided in such apparatus.
FIG. 7 shows a prior art digital voice messaging apparatus. A signal from a microphone 806 or other analog signal source is input to a codec 804 for conversion to .mu.-law or A-law pulse code modulated (PCM) data. The .mu.-law or A-law PCM data is output to an encoder/decoder functional block 803 including a voice compression encoder 803a and voice compression decoder 803b. The codec 804 also receives PCM data from the voice compression decoder 803b and converts that PCM data into an analog signal for output to and playback by a speaker 808.
The voice messaging system may be a multiple user system with partitions in voice message memory corresponding to the plurality of users. Moreover, the individual components of the digital voice messaging system may be multiple channel devices capable of handling individual user voice mailboxes.
A processor 802 controls the encoder 803a and decoder 803b. Processor 802 also controls storage of the compressed (encoded) speech data from the voice compression encoder 803a into memory 800, and controls the retrieval of compressed speech data from memory 800 and output of the same to the voice compression decoder 803b, based on user selections at the message controls 810. Conventional message controls include PLAY, RECORD, FAST FORWARD, and REWIND.
Old messages are deleted from voice mailboxes or personal voice message systems in any of a multitude of ways. For instance, in some systems rewinding to a chronological point before a particular stored voice message effectively deletes all subsequently stored voice messages. However, these deletions must be performed for each message or group of messages stored. The deletion of stored messages is not automatic in conventional systems.
FIG. 8 depicts the utilization of memory 800 after the storage of an example maximum number of voice messages 601-605 of given lengths. Initially, no voice messages are stored in memory 800. Thereafter, a first message 601 is received by the voice messaging system relating to a particular mailbox or phone number, and is stored in memory 800. The first message 601 uses a small percentage of the full capacity of the memory 800 as depicted with respect to the vertical axis of FIG. 8. At the time that the first message 601 is stored in memory 800, most of the memory 800 is available for storage of voice messages.
When a second message 602 is received by the voice messaging system, it is stored in memory 800 in addition to the first message 601 which was previously stored. The third message 603, the fourth message 604, and the fifth message 605 are subsequently and similarly stored in memory 800 when received. As depicted in FIG. 8, the memory usage is nearly at capacity (i.e., 100%) after storage of the fifth message 605.
Storage of a sixth message 600 is cut-off because it exceeds the available voice message memory. Thereafter, no new messages can be stored in memory 800 until at least one of the previously-stored older messages 601-605 is deleted, freeing up some memory. Even then, if a voice message is longer than the freed-up memory, its storage in memory will be cut-off without the entire voice message being stored.
The maximum number of voice messages which can be stored in memory 800 is a direct function of the efficiency of the encoding and decoding techniques utilized in the encoder/decoder functional block 803, and the size of the memory 800. Generally, the larger the memory 800, and the more efficient the encoding technique, the greater the number of messages that can be stored in the digital voice messaging system.
When the memory 800 becomes nearly filled with messages, no new messages are allowed to be stored until old messages are manually deleted. Conventional digital voice messaging systems will not answer an incoming call if there is no available memory for storing a new message. This `lock-out` feature ensures that old messages will not be deleted without being heard by the user. However, many users of voice messaging machines listen to messages and then do not delete the messages afterwards. This eventually results in an incapacitated voice messaging system which will not store any new voice messages until some amount of memory 800 is freed-up. The conventional way to free-up memory is to delete previously stored, old voice messages.
There is a need for a voice messaging system which, without manually deleting old voice messages, gives the user a balance between the ability to retain older messages and accepting new messages after the memory of the voice messaging system is full.